Lloyd Blankfein, the chief executive of Goldman Sachs, has attacked the Securities & Exchange Commission’s fraud charges against the Wall Street titan in a series of telephone calls to clients, the Financial Times reported, as the firm sought to protect its damaged reputation.

The newspaper said that one person who received a call from the Goldman chief said he was told the regulator’s case against the bank was politically motivated and would ultimately “hurt America”.

Meanwhile, media reports said that Blankfein has been summoned by Congress to testify about the fraud, which has reignited debate on whether big, integrated banking groups should be forced to split off their trading activities to help prevent potential conflicts of interest. The affair has become an international one: the Financial Services Authority, the UK regulator, launched its own investigation into Goldman Sachs’ activities earlier this week.

Lawyers are already predicting that the alleged fraud, which surrounds how Goldman went about selling securities linked to the US subprime mortgage market, will trigger a wave of lawsuits from investors. Goldman is accused of selling a package of collateralized debt obligations to investors without telling them that renowned hedge fund firm, Paulson & Co, which made money by short-selling such products, was simultaneously involved in selecting securities in the CDO.

In the conversations with private equity executives and others, Blankfein left clients with the impression that he was eager to fight the charges in court, the publication said.

“He was very aggressive,” one person called by Blankfein was quoted as saying. “He feels that the government is out to kill them, that they are under attack and the whole thing is totally political.”

Blankfein said the SEC action “hurts America”, this person said.

The CEO is due to testify before a Senate panel next week, media reports said. Blankfein will answer questions before the Senate's Permanent Subcommittee on Investigation.